On Fri, Oct 07, 2022 at 09:58:31AM +0200, Thomas Zimmermann wrote: > Hi > > Am 07.10.22 um 09:15 schrieb Ville Syrjälä: > > >> > >> For the absolute size of fbdev memory, I think we should introduce a > >> module parameter in drm_fb_helper, which an option to set a default > >> value in the kernel config. It would benefit all drivers that use fbdev > >> emulation and work how overalloc works. > >> > >> If no size is given, the current approach would be used. > >> > >> I don't think resizing would work immediately. There isn't anything in > >> the check_var and set_par functions that implements the necessary atomic > >> check and commit. > > > > set_par() is the thing tht does the commit. > > > > I know. There actually even is a commit statement in set_par, which can > restore the initial mode. My point is that it has no means of changing > the display mode. A full modeset would require us to convert the fb > screeninfo into an atomic state and commit that instead. For the fbconv > helper, I once made code to convert between the two. Leaving this here > for reference. [1][2] Uff. Right, we'd probably just want to properly implemnt set_par() then. BTW I had a slightly different take on the bitfiled stuff. Maybe a bit easier to extend for new formats, but full of macros: https://patchwork.freedesktop.org/patch/203189/?series=37820&rev=1 > > Similarly, in check_var we sort out and reject all mode changes. We'd > have to change that as well. I guess we could do a TEST_ONLY commit there. Though I think not doing that and just failing from set_par() should be fine too. > > I guess we can continue to ignore non-atomic modesetting. > > Best regards > Thomas > > [1] > https://gitlab.freedesktop.org/tzimmermann/linux/-/commit/385161cd2d048b5cf80544bff8ced3da7a82dfa9 > [2] > https://gitlab.freedesktop.org/tzimmermann/linux/-/commit/a541c405a638f47ee80389b222fbde6e311e8220 > > -- > Thomas Zimmermann > Graphics Driver Developer > SUSE Software Solutions Germany GmbH > Maxfeldstr. 5, 90409 Nürnberg, Germany > (HRB 36809, AG Nürnberg) > Geschäftsführer: Ivo Totev -- Ville Syrjälä Intel
